<select name="" <?=$estilo;?> onchange="MM_jumpMenu('parent',this,0)">
    <?php
    for($x=1;$x<=20;$x++){
    ?>
    <option value="?qtd=<?=$x;?>" <?php if($qtd == $x) { echo "selected"; } ?>><?=$x;?></option>
    <?php } ?>

</select>
<input type="hidden" name="qtd" value="<?=$qtd;?>">